Hypoid gear lubricants for slip-lock differentials



United States Patent 3,211,647 HYPOID GEAR LUBRICANTS FOR SLIP-LOCKDIFFERENTIALS Rosemary OHalloran, Union, and Louise K. Armington,

Roselle, N .J., assiguors to Esso Research and Engineering Company, acorporation of Delaware No Drawing. Original application Dec. 31, 1958,Ser. No. 784,044. Divided and this application Apr. 19, 1961, Ser. No.104,018

7 Claims. (Cl. 252-32.7)

This application is a divisional application of U.S. Serial No. 784,044filed December 31, 1958.

This invention relates to the discovery that certain amines or aminederivatives when added to gear lubricants, eliminate or markedly reducethose noises which frequently occur in the clutch plate assembly of thenewly introduced slip-lock differentials for automotive vehicles. Thisinvention also relates to the discovery that gear oil blends designedfor very severe operating conditions (high speed, high torque or severeshock) may be rendered suitable for use in slip-lock differentialswithout objectionable noise and without any loss in extreme pressureproperties by the addition of minor amounts of an amine and anazomethine. This invention therefore relates to a method for eliminatingthose noises which frequently occur in conventionally lubricatedslip-lock differentials and to the gear lubricating compositionssuitable for use in slip-lock differentials that are produced thereby.

There are a wide variety of conventional gear oils entirely satisfactoryfor lubricating differentials. However, when these conventional gearoils are used to lubricate slip-lock differentials, in many cases anoisy chattering occurs in the clutch plate assembly of the slip-lockdifferential under certain conditions which occur in normal driving. Theslip-lock differential units for automotive rear axles consist of a packof 3 to 5 discs or plates mounted on each axle which act to retard themovement of the faster running wheel (as when one wheel is slipping onmud or ice) and to direct torque back to the other wheel, i.e., when onewheel begins to slip, the clutch plates upon that axle are engaged toretard the movement of the slipping wheel and thus direct torque to thenonslipping wheel. This enables car to move in situations where aconventional differential would continue to allow the torque to betransmitted to the slipping wheel. It has been found through testing onnumerous cars equipped with these slip-lock differentials that on sharpturns the clutch of the axle of the wheel on the outside arc of the turnwill be partially engaged, causing chattering and thudding sounds thatcreate a vibration throughout the entire car. This noise or vibrationoccurs frequently enough in general car operation to be annoying to thedriver and disturbing to the automobile manufacturers. Properlubrication of the slip-lock axles requires a lubricant containing (a)an extreme pressure agent to prevent wear of the highly loaded hypoidgears, and (b) a lubricant which will prevent or reduce the noise of theclutch plates when they are engaged and especially when they arepartially engaged as when making sharp turns.

It has now been found and this finding forms the basis of the presentinvention, that certain amines or amine derivatives when added to gearoils completely remove or markedly reduce this objectionable clutchplate chatter. These amine-gear oil blends continue to give entirelysatisfactory performance in standard differentials in addition to givingquiet performance in the newly introduced slip-lock differentials. Theamine additives of this inven tion are particularly effective in gearoils compounded from lubricating oils having a viscosity of about to 220SUS at 210 F. and containing extreme pressure additives such assulfur-chlorine and P=S=Cl containing compounds. However, in gear oilsdesigned for extremely severe operating conditions (high speed, hightorque or severe shock) as are gear oils designed for use in militaryvehicles (i.e., gear oils passing MIL-L-2105 and more severe tests), theamines of this invention have been found to reduce the ability of thesegear oils to pass severe gear tests. Thus, as a further facet of thisinvention it has been found that addition of an azomethine in additionto the amine will improve the ability of these high performance gear oilblends to pass severe gear tests of the type required for militaryapproval. At the same time the amine-azomethine blend imparts quietperformance to these high performance gear oils when used in slip-lockdifferentials.

In brief compass, the slip-lock differential lubricants of thisinvention will comprise a major proportion of a gear oil compounded froma lubricating oil or base oil having a viscosity of about 50 to 220 SUSat 210 R, an extreme pressure additive, and in the range of 0.2 to 2.0wt. percent of a primary C to C alkyl amine. The slip-lock differentiallubricants designed for extremely severe operating conditions (highspeed, high torque or severe shock) will comprise in the range of 0.15to 1.5 wt. percent of a C to C aliphatic azomethine in addition to theabove ingredients, the ratio of amine to azomethine being about 0.25 to4.0.

The amine additives of this invention include primary alkyl amines,wherein the alkyl group is a branched or straight chain alkyl group of aC to C hydrocarbon. A mixture of primary alkyl amines may also be used,such as the primary alkyl amines made from hydrogenated tallow. Examplesof operable amines are octadecyl, hexadecyl, octadecenyl and dodecylamines. The primary alkyl amines of 12 to 24 carbon atotms arepreferred, and mixtures of the primary alkyl amines made fromhydrogenated tallow are particularly preferred.

The azomethine additive is prepared by reacting formaldehyde with analiphatic amine and has the following generic formula:

wherein R represents an alkyl or alkenyl group of 12-24 carbon atoms andpreferably 14-16 carbon atoms. Particularly preferred are theazomethines, wherein R is a tertiary alkyl group of 14-16 carbon atoms.The preferred species of R is derived from propylene polymer. Thereaction between the alkyl amine and formaldehyde is shown in thefollowing equation:

Suitable azomethines have a carbon to hydrogen ratio of about 5.6, anitrogen content between 5.5 and 7% by weight and carbon content between-75 and 85% by weight by ultimate analysis.

The base oil used to form the gear lubricants of this invention may beeither a mineral or a synthetic lubricating oil, the former beingpreferred. These lubricating oils will have a viscosity in the range of50 to 220 SUS at 210 F. and a viscosity index in the range of 20 to+150, preferably in the range of 60 to 100.

The gear oil for use in accordance with this invention may containconventional "additives, such as viscosity index improvers, antioxidantsor corrosion inhibitors, and normally contains extreme pressure" agents,such as chlorinated paraffins, lead soaps, zinc dialkyl dithiophosphate,sulfurized oils, etc. Extreme pressure additives are well known in thelubricating art and are normally used in hypoid gear lubricants. Thusthe, compositions of the invention may contain 1 to 20 wt. percent of asulfurand chlorine-containing paraffinc hydrocarbon having in the rangeof 3 to 10 wt. percent of sulfur and about 10 to 40 wt. percent ofchlorine. They may also contain 1 to 20 wt. percent of a zinc dialkyldithiophosphate having 3 to 20 carbon atoms per alkyl group. Theincreased rear wheel torque of new passenger cars and commercialvehicles has caused a corresponding increase in the loading on thehypoid gears and has necessitated the use of lubricants containingextreme pressure agents. 7 The additives of this invention may beprepared in concentrated form. For example,about 2 to 20 Wt. percent ofthe amine or 2 to 20 wt. percent of the amine and 1.5 to wt. percent ofthe aliphatic azomethine may be added to a gear oil base to form theconcentrate.

In general, the compositions of this invention will be prepared bysimply adding the amine or the amine and azomethine to the gear oilbase.

The invention will be further understood by the following examples whichinclude the preferred embodiments of the invention.

EXAMPLE I To show that certain amines or amine derivatives substantiallyreduce or eliminate those noises which frequently occur in slip-lockdifferentials, a mineral lubricating oil (base oil) and three difierentgear oils were tested with and without the amine additives in differentmake automobiles equipped with slip-lock difierentials. A conventionallylubricated slip-lock diiferential produces frerepresentative of avariety of relatively severe conditions to show graduations ofperformance.

The oils used in the following tests were:

Base 0il.A mineral lubricating oil having a viscosity at 210 F. of about94 SUS and a viscosity index of 90 consisting of a blend of (1) dewaxed,deasphalted residuum having nominal viscosity at 210 F. of 210 SUS and(2) dewaxed, phenol extracted clay-contacted distillate of nominalviscosity at 100 F. of 250 SUS, each component being derived fromMid-Continent crude.

Gear oil A.A base hypoid gear lubricating oil composition prepared bymixing 6.4 wt. percent of a sulfurchlorinated paraffin and 5.2 wt.percent of a zinc dihexyl dithiophosphate (the hexyl groups were derivedfrom methyl isobutyl carbinol) in 88.4 wt. percent of a minerallubricating oil having a V.I. of 90 and a viscosity at 100 F. of 1094SUS. The sulfur-chlorinated paraffin was prepared according to US.2,124,598 and contained 30 wt. percent chlorine and 6 wt. percentsulfur. The zinc dihexyl ditiophosphate used above was preparedaccording to U.S. 2,369,632.

Gear oil B.A hypoid gear lubricating oil composition consisting of 10wt. percent of the sulfur-chlorinated parafiin of gear oil A in theabove base oil (viscosity index of 90 and a viscosity at 210 F. of 94SUS).

Gear oil C.--A hypoid gear lubricating oil consisting of 3.05 wt.percent of the sulfur-chlorinated parafiin of gear oil A and 2.48 wt.percent of the zinc dihexyl dithiophosphate of gear oil A in the abovebase oil (viscosity index of 90 and a viscosity at 210 F. of 94 SUS).

Table I which follows shows, first, that slip-lock difi'erentials arenoisy with (1) base oil (Run 1), (2) conventional sulfur-chlorinatedtype gear oils (gear oil B, Run 3), and (3) with MIL-L-2105 type oils(gear oil A, Run 7); second, that certain conventional lubricity oroiliness agents do notimprove performance (Runs 4, 5, 8, 9, 10 and 11);third, the Amine T (a mixture of primary alkyl amines consisting of 30%hexadecyl amine and octadecyl amine) gives marked reduction orcompleteelimination of noise (Runs 2, 6, l2 and 13); and, fourth, that amixture of Amine T and Azomethine J (a C alkyl azomethine) is alsoeffective in markedly reducing noise (Run 14).

The road tests of Table I were con-ducted by executing tight circles atspeeds 'of from about 2 to 10 miles per hour with braking during thecourse of the turn.

Table 1 Noise on Sharp Turn with Braking Runs Additive, Wt. Percent GearOil Chrysler DeSota Pontiac None Base Oil. Severe 1% W17. Amine T- 0None Nmw B Severe 0.25 wt. percent TOP B Do. 0.5 wt. percent TOP..- BDo. 0.5 wt. percent Amine T B None None A. Severe. 25 percent sulfurizedSperm A do 1 0.5 wt. percent Castor Oil 0.25 wt. percent DimerizedLinoleic Acid. 0.5 wt. percent TOP 1.0 wt. percent Amine '1 0.5 wt.percent Amine T A 0.33 Amine T plus 0.14 Azomethine .T.

[All tests were made in the same 1958 Chrysler within a one-week period.Each oil was quent and extremely annoying chattering sounds duringnormal operation; however, for test purposes the most severe conditionsare used so that the noise is at its worst level. Thus, changes in noiselevel may be apparent. Data in Tables I and III which follow wereobtained used for at least 7 miles before start of testing] Table IIshows that other amines and amines salts'also give a definiteimprovement in the noise level. Results indicate that oils formulatedwith these other additives would be satisfactory in all-but the mostcritical cars on the road under normal operating conditions. The tableunderthe most severe conditions. Data in Table II are also shows thatthe primary alkylamines are preferred.

Table II [All tests were made in the same 1958 Chrysler within a oneweekperiod. Each oil was used for at least 7 miles before start of testing]Slip-Lock Noise Rating 1 Soya dimethyl amine, i.e. a tertiary amineRN(CH3). 2 Dioleate of N-tallow propylene dlamlne.

Table III shows the ability of various amine additives in variedconcentrations to suppress slip-lock chattering.

chlorinated pai'aifin and 5.7 wt. percent of the zinc dihexyldithiophosphate were added to the base oil. The

The table also shows that while azomethine by itself is extreme presscreproperties of gear oil D were tested not effective in preventing noisein slip-lock differentials, alone and with different additives by meansof an SAE it performs satisfactorily when combined with primary ExtremePressure Testing Machine (CRC designation,

alkyl amines. Further, the table establishes that amines L-17-545). SeeCoordinating Research Councils Handand particularly primary amines inconcentrations above book, 1946; copyright, 1946; by CoordinatingResearch 0.3 wt. percent based on the weight of the gear oil blend,Council, Inc., and published by J. J. Little and Ives Comeither alone orin combination with alkyl azomethines pany, New York. In brief, thistest consisted of rotating will substantially reduce chattering inslip-lock differtwo cylindrical test specimens in line con-tact witheach entials. The tests are particularly designed to determine other andin opposite directions with pressure applied the ability of the additiveto suppress the chattering noises at the line contact between therotating cylinders. A which occur on sharp turns at speeds of about 5 to15 -pound load was applied for a 15-minute break-in miles per hour.Partial engagement of the clutch plates period, followed by increasingthe load to 110 pounds and on the axle of the outside wheel (relative tothe turn) rotating the test cyclinders for one hour at 225 F. The occursunder these conditions. shaft was operated at 500 r.p.m. with a gearratio of 3.4 to

Table III. Slip-lock difierential noise tests Noise on Left Circles withBraking Additive Gear Wt. percent Oil in Gear Oil 58 DeSoto 68 Chrysler58 Chev. 58 Olds.

None..- Severe Severe Severe Severe. Amine SaltD A 0.5 Very light A 1.0None A 0.1 Severe A 0.3 .do A 0. 5 Very light--. Moderate. A 1.0 A Verylight.-.

A 0.7 None None.

0.3 C 0.33 Trace EXAMPLE II 1 between the test cylinders and the shaft.The weight As pointed out in the Specification amine containing loss, inmilligrams, of the test cylinders was then measured.

gear oil blends are not quite as good in extreme pressure 55 T able IV.Modified SAE test P PP i116 Oflglnal gefflr That iaddltlon of a[15-minute break-in with 55-pound load, plus 1 hour at 225 F. with 110-primary amine causes a slight increase in wear as do poundload otheramines and amine derivatives. However, azomethine reduces wear and whenadded to amine/gear oil i g Rings, blends imparts a wear resistancesuperior to that of the Additive Wt percent gear 011 without aminedespite the adverse effect, as 111 011 Top Bottom regards wear, of theamine when used alone in the gear 0 63 15 Table IV shows that the aminesof Table II when added 0. 5 Sparks, heavy scoring to high performanceMIL-L-2105 type gear oils, will %-8 g1 reduce the extreme pressureproperties of said gear oils. 123 34 The table further shows, however,that if an alkyl I 8-2 i8 azomethine or a combination of an alkylazomethine and Amine T and Azomethme J 11 12 an amine is added to thesame gear oil the extreme pres- D0 8-? 18 20 sure properties, instead ofbeing decreased, will actually 7 1 be improved.

Table IV represents the results obtained in a modified i Amine D isanN-alkyl propylene diemi'he wherein the alk group is SAE test. The baselubricant for this test was a hypoid 25352;? g f' gfig g gi gg gfl g igf gi ggg gg and a C18 11101101111- geal' hflreinafier designated g 011D, Whlch was the 2 Same as Amine Salt D of Table II (dloleate ofN-tallow propylene same as gear oil A except that 6.9 wt. percent of thesulfur- To confirm the laboratory data of Table IV full-scale gear testswere conducted on gear oil A alone and on gear oil A containing thoseadditives which successfully prevented chattering noises in the roadtests of Tables I, II and III above.

The full-scale gear tests consisted of:

(l) CRCL-37756 high speed-high torque test..The CRCL37-75 6 test wasdeveloped for the Ordnance Department and is titled, Research Techniquefor Determining Load Carrying, Wear, and Extreme PressureCharacteristics of Universal Gear Lubricants in Axles Under Conditionsof High Speed, Low Torque Operation,i

Followed by Low Speed, High Torque Operation. Briefly described, thistest is carried out as follows:

The test unit consists of a new %-ton army truck hypoid rear axlecarrier, 5.83:1 ratio, installed in its own housing. The unit is drivenby a six-cylinder, 235 cu. in. Chevrolet truck engine with standardignition and carburetor, with suitable transmission, couplings, anddynamometer parts.

Sequence 1 of the test consists of 100 minutes opera tion at a ring gearspeed of 440 i 5 rpm. and a ring gear torque of 9460 i 150 inch-pound.The gear oil temperature is 300 F. maximum.

Sequence 2 of the test consists of 24 hours operation the presence ofair. .Upon cooling, the percent viscosity increase at 210 F. and thesludge as percent sediment insoluble in heptane were determined. Theresults are at a ring gear speed of 80:1 r.p.m. and a ring gear torqueof 41,800 i 150 inch-pound. The oil temperature is 275 F. 3 F.

After completion of the above test, the ring and pinion gears areexamined for evidence of surface distress and wear. The results of theabove tests are shown in Table V which follows.

(2) Buick 10-A road test.The Buick l0-A test is an actual road test andconsists of 10 high speed cycles of driving from 60 to 109 m.p.h., 3shock cycles at 50 to 35 m.p.h., 60 to 45 m.p.h., and 70 to 55 m.p.h.,respectively, followed by 10 more high speed cycles of 60 to 109 m.p.h.The high speed cycles were carried out by rapidly accelerating from 60to 109 m.p.h., then allowing the auto to coast until the speed was backto 60 m.p.h., then the cycle was repeated. The shock cycles were carriedout by allowing the auto to coast from the higher speed until the lowerspeed was reached and then shifting into low gear. Upon completion oftest, the differential was disassembled and the ring gear and piniongears examined for scoring.

Table V.Full-scale gear tests Buie 10-A Road Shock Test, Percent ScoreORG-L-37 Test High Test Oils, Additives,

Speed, High Torque Wt. Percent; in Gear Oil A None 0.5 Amine T 0.5 Amine'1 plus 0.25 tricresyl phosphate.

0.7 Amine '1 plus 0.3

Azornethine J.

0.5 Amine T plus 0.25

Azomethine J .5 Amine T plus 0.5

dioetyl acid phosphate.

Very light. ridging 5-10 (interpolated). Fail, light ridging. Pass, 5.

Fail, medium rldging Borderline, 10.

Pass

Pass, 3.

Fail, light-medium ridging.

It has also been found that the primary alkyl amines and theamine-azomethine additives of this invention are effective in improvingthe high temperature stability of gear oils. To illustrate this propertysamples of gear oil A containing (1) no additive, and (2) Amine T andAzomethine J, were heated for 100 hours at 250 F. in

shown in Table VI.

Table V\I.Gear oil oxidation tests Hrs. at 250 F.]

It is evident that the additives of this invention, when used in totalconcentrations of 0.75 to 1.0% in gear oil A, are effective not only incontrolling the increase in viscosity but also in preventing theformation of sediment upon oxidation.

In summary, Examples I-III show that addition of minor amounts of anamine will suppress the noise in slip-lock differentials, reduce sludgeformation on storage, and when combined with an azomethine will improvethe extreme pressure properties of the lubricant.

Use of the additive and additive combination of this invention shouldnot be limited to the above examples.

What is claimed is:

1. A lubricating composition suitable for use as a gear lubricantcomprising a major proportion of a hydrocarbon lubricating oil, 0.2 to2.0 wt. percent of an oil soluble compound selected from the groupconsisting of C to C alkyl amines and the higher fatty acid saltsthereof, and 0.10 to 1.5 wt. percent of a C to C alkyl azomethine.

2. A lubricating composition according to claim 1 which also contains 1to 20 wt. percent of a sulfurand chlorine-containing paraifinichydrocarbon having in the range of 3 to 10 wt. percent sulfur and about10 to 40 wt. percent chlorine.

3. A lubricating composition according to claim 2 which also contains 1to 20 wt. percent of a zinc dialkyl dithiophosphate having 3 to 20carbon atoms per alkyl group.

4. A concentrate gear oil additive, for use in lubricating slip-lockdifferentials, comprising a major proportion of a mineral lubricatingoil having a viscosity in the range of 50 to 220 SUS at 210 F. and aviscosity index of about 20 to +150, a minor amount, in the range of 2to 20 wt. percent of a primary C to C alkyl amine and about 1.5 to 15wt. percent of an azomethine having the formula wherein R is selectedfrom the group consisting of C to C alkyl groups and C to C alkenylgroups, the ratio of amine to azomethine being about 0.25 to 4.0.

5. A lubricating composition suitable for use as a gear lubricantcomprising a major proportion of a mineral lubricating oil, 0.2 to 2.0wt. percent of a primary C to C alkyl amine and 0.10 to 1.5 wt. percentof a C to C alkyl azomethine.

' 6. A lubricating composition according to claim 5 wherein saidazomethine is a C to C alkyl azomethine.

7. A concentrate gear oil additive, for use in lubricating slip-lockdifferentials, comprising a major proportion of a hydrocarbonlubricating oil having a viscosity in the range of 50 to 20 SUS at 210F. and a viscosity index of about --20 to a minor amount, in the rangeof 2 to 20 wt. percent of a primary C to C alkyl amine, and about 1.5 to15 wt. percent of an azomethine having the formula RN=CH wherein R isselected from the grou consisting of C to C alkyl groups and C to 9 10 Calkenyl groups, the ratio of amine to azomethine 2,369,632 2/45 Cook eta1 252-332 X being about 0.25 to 4.0. 2,611,766 9/52 Schneider et a1.25248.8 X 2,758,086 8/56 Stuart et a1 25250 X References Cited y theExaminer 2,832,741 4/58 Gottshall et a1. 252-50 UNITED STATES PATENTS 5DANIE MAN, P 1,594,983 8/26 Somerville 2s2- so L E WY Examme' 2,364,28312/44 Freuler 252-327 JULIUS GREENWALD, Examiner-

1. A LUBRICATING COMPOSITION SUITABLE FOR USE AS A GEAR LUBRICANTCOMPRISING A MAJOR PROPORTION OF A HYDROCARBON LUBRICATING OIL, 0.2 TO2.0 WT. PERCENT OF AN OIL SOLUBLE COMPOUND SELECTED FROM THE GROUPCONSISTING OF C12 TO C24 ALKYL AMINES AND THE HIGHER FATTY ACID SALTSTHEREOF, AND 0.10 TO 1.5 WT. PERCENT OF A C12 TO C24 ALKYL AZOMETHINE.2. A LUBRICATING COMPOSITION ACCORDING TO CLAIM 1 WHICH ALSO CONTAINS 1TO 20 WT. PERCENT OF A SULFUR-AND CHLORINE-CONTAINING PARAFFINICHYDROCAARBON HAVING IN THE RANGE OF 3 TO 10 WT. PERCENT SULFUR AND ABOUT10 TO 40 WT. PERCENT CHLORINE.
 3. A LUBRICATING COMPOSITION ACCORDING TOCLAIM 2 WHICH ALSO CONTAINS 1 TO 20 WT. PERCENT OF A ZINC DIALKYLDITHIOPHOSPHATE HAVING 3 TO 20 CARBON ATOMS PER ALKYL GROUP.